A GeoSonics/Vibra-Tech Iso-Seis evaluation gives you the whole story behind your vibration footprint, so you can keep your operation on solid ground.
Vibration from blasting produces wide-ranging vibration perception. While seismographs can ensure and demonstrate compliance, community reviews and public meetings require more advanced analysis. GeoSonics/Vibra-Tech developed the Iso-Seis program to contour vibration levels using multiple instruments distributed over the adjacent community. Measurements from up to 150 individual recording units provide demonstrable vibration data for evaluating a single blast and show the vibration as it is affected by geology and pattern development. Iso-Seis allows an operations manager to assess ground vibration attenuation, determine specialized geologic features that affect vibration and evaluate community complaints in one operation.
Ground vibration reduction with distance evaluations may be completed with multiple blast evaluations and projections based upon regression analysis. The goal of the Iso-Seis program is to take attenuation to a significantly greater and more accurate level. The vibration contouring shows the maximum attenuation of the geology and can indicate the presence of “hot spots” or areas where vibration may affect soil profiles differently. Ultimately, whether construction, mining or quarrying, vibration levels are more accurately predicted.
In addition to standard blasting, the effects of modifications to the blasting patterns can be assessed. By modifying loading parameters, the vibration changes may be visually seen and demonstrated. This includes loading, pattern orientation and delay sequences. Combined with Vibra-Map, delay selection programs maximize your blasting operations.
Put theory into practice. GeoSonics/Vibra-Tech’s custom mapping analysis helps you reduce ground vibration and get more out of your blasting holes.
GeoSonics/Vibra-Tech’s Vibra-Map is the original delay selection program available for commercial evaluation of blasting delays. Based in scientific wave motion theory, the analysis performed is designed to reduce ground vibration and can subsequently improve blasting fragmentation in the pit through the efficient design of blasthole detonation.
Blasting vibration is driven by the maximum pounds per delay detonated within milliseconds. For single hole blasts the blast is over and done. However, with multiple holes and multiple deck blasts, the overlapping patterns can reinforce the initial detonation wave, amplifying the resulting vibration. This causes higher ground vibration at off-property structures and increases complaints. It may also increase the low-frequency content of the waves generated, affecting the natural response of the adjacent structures and further increasing complaints. Longer duration delays cause structures to respond longer and with more effects. Delay selection to change frequency and affect off-site structure response is critical.
The Vibra-Map program uses single hole signature blasts for initial wave generation. With mapping and mathematical evaluation of the wave motion, time periods may be developed where cancellation of vibration pulses is achieved. While zero vibration is not possible, significant reductions in the motion can be achieved and provide a significant reduction in off-site motions.
Vibra-Map successes indicate reduction in vibration energy at the low natural frequency of the site. The reduction in energy at the natural frequency of the site helps reduce off-property concerns about ground vibration. The reduction in energy at the low natural frequency of the site alters the response of the structure, decreasing the amplification from ground motion into the building. This significant change has been responsible for reducing complaints and taking vibration levels out of the range of highest damage potential when compared to U.S. Bureau of Mines limitations. Further measurement and testing with Iso-Seis demonstrates successful results.
Whether mining, quarrying or constructing, vibration solutions aren’t one size fits all. GeoSonics/Vibra-Tech is your resource for the most complete overall site evaluation.
There is no single ground vibration reduction solution for mining, quarrying and construction sites. GeoSonics/Vibra-Tech’s attenuation studies can evaluate your overall blasting program and provide all the solutions you need – from technical to public relations.
Vibration is an issue any time blasting operations are in close proximity to neighbors. In such cases, companies often spend considerable time and resources on community relations, but efforts will fall short if there’s a lack of attention to off-site ground vibration and airblast from blasting. Third-party evaluation rooted in GeoSonics/Vibra-Tech’s 60 years of experience can greatly enhance the credibility of your evaluation.
Using evaluations of blast data with regression analysis for ground vibration and airblast, GeoSonics/Vibra-Tech can establish trends and assess vibration concerns. Where multiple blast locations and benches create varying results due to geology, pattern orientation, depth and loading configuration, our evaluations can provide answers to those concerns. When internal data is insufficient, GeoSonics/Vibra-Tech can also plan and execute ground vibration measurements to develop site-specific data.
For advanced analysis, our Vibra-Map and Iso-Seis evaluations further the on-site technical data and can demonstrate successful blasting program modifications to communities, regulators and management. Continual measurement programs and web-based results can provide real-time evaluations and further emphasize your responsiveness to the community.
Structural Response Studies
GeoSonics/Vibra-Tech’s advanced instrument and comprehensive structure studies are key to making short work of community complaints and compliance concerns.
Low peak particle velocity does not always mean no complaints. People complain about blasting operations for a number of reasons unrelated to ground vibration or airblast, but underlying every complaint is a fear of damage to homes or buildings. The perception of vibration and airblast is typically produced by the structure response to outside forces. Each state, county or city has regulations maintaining levels within limits, but that does not always stop complaints or claims of damage. In such cases, structure response evaluations are completed to ensure that structures are not adversely affected and are not responding in an unexpected manner, and to allow for modifications to blasting plans.
Blasting studies show that racking of the structure and bending of interior walls occur as vibration occurs. In special circumstances multi-story structures will respond differently to outside stimulus. Showing and documenting these effects can demonstrate to regulatory agencies and property owners the impact on their structures.
While a structure has a normal response, further evidence may be necessary to show that vibration is not affecting it, such as crack monitoring. GeoSonics/Vibra-Tech has advanced level instrumentation to show the behavior of cracking in structures. Crack width changes relate directly to crack length, so measurement of width changes shows whether length will change.
GeoSonics/Vibra-Tech’s Re:mote Monitoring systems use crack gauges to measure width and produce recordings that indicate motion and can be used with vibration measurement to show blast vibration stresses. Continual environmental monitoring shows long-term changes produced by temperature and humidity. Mounted on the interior or exterior of structures, the gauges track motion of any type, producing a record to show that vibration is not causing the stress on a structure that would cause defects.
Overall, the motions of the structure are key to making short work of complaints and demonstrating compliance.
Want a second opinion? Count on the expert staff at GeoSonics/Vibra-Tech to thoroughly review all your blasting best practices.
Issues surrounding blasting can be reduced when accurate results and records are maintained and drilling and blasting procedures are documented. External blasting audits can maintain the integrity of your blasting program by putting a third-party review in place. GeoSonics/Vibra-Tech’s qualified staff can provide thorough third-party auditing, including:
- Ensuring complete accuracy of your blasting records.
- Ensuring vibration monitoring procedures are correct:
- Is the seismograph set up consistently each time?
- Are the vibration records electronically stored or printed and maintained with the blasting logs for each and every blast?
- Is the seismograph at the correct location based on local regulations?
- Ensuring safety procedures are followed for blasting operations:
- Is drilling done within guidelines?
- Are blasters and helpers correctly planning and preparing the blast site?
- Are safety procedures taken for loading and wiring?
- Is the blast site cleared properly and are the correct and proper warning signals sounded prior to detonation?
Blasting Impact Analysis
Know your limits. A GeoSonics/Vibra-Tech pre-blast evaluation can make easement access easier and reduce strain on your new construction dig site.
The construction of new structures to expand living quarters has given rise to a new problem for construction and utility companies. The law states that “positive easements” (easements that can be used to run pipes or cables under ground) must be of a specified width. For this reason, new pipelines or utility lines must be placed in the same easement as the existing lines. To get to these lines, excavation of the ground is necessary. The fastest and most economical means of achieving this is blasting – except that vibration induced by blasting could be detrimental to the existing utility and pipelines.
Incidents involving pipelines are extremely rare. During the last 10 years, there have only been a few injuries from incidents involving pipeline facilities. However, the majority of those injuries were to people digging or working on or around the lines. Most utility and construction companies have to take precautions to avoid injury and damage to the pipeline. GeoSonics/Vibra-Tech can help with techniques designed to calculate the allowable stress and monitoring procedure which can be applied on a utility line near explosive detonation. Our techniques greatly decrease potential damage to utility lines induced by detonation of explosives.
Dynamic Crack Monitoring
GeoSonics/Vibra-Tech takes the mystery out of crack movement with an easy-to-understand approach that answers the question, “Did the crack get bigger or not?”
The digital crack gauge is a valuable tool for measuring the movement of a cosmetic or structural crack during vibration causing events. GeoSonics/Vibra-Tech’s crack gauge systems yield both comprehensive dynamic and environmental information on crack displacement. Dynamic data (recorded during a vibratory event) is essential for determining a crack’s activity during excitation. Our crack gauge systems, which can measure crack movement with a resolution of 0.000004 inch, show if there is any correlation between crack movement and other vibration producing activities.
Early crack monitor methods could falsely confirm that a crack was inactive, unless drastic shifts occurred. Our Re:mote Digital Crack Gauge System collects and records evidence of these changes in a time-history waveform that is valuable in correlating crack movement with other activities like blasting, construction and pile driving. Environmental data (long-term structural changes) are also recorded for comparison to reactions from excitation. Environmental factors are constantly exerting a significant and measurable force on structures. While these forces are small, their effects are cumulative and add up to visible crack movement over time. Research shows that environmental movement from temperature and relative humidity changes typically exceeds movement from most vibratory sources by a large margin.
The accuracy of our crack gauge system also gives it value as a public relations tool. Concepts like particle velocity and air overpressures are often hard to explain to people without industry expertise. Digital crack gauges take the mystery out of crack movement, providing clear, easy-to-understand answers to the question, “Did the crack get bigger or not?”